Bug: `macos_application` with `macos_extension` fails because of missing `extension_host`

Description

Related to: https://github.com/MobileNativeFoundation/rules_xcodeproj/issues/2937

When using macos_application that has extensions the project generation fails with:

ERROR: Custom scheme "TophatExtension"'s run launch target (@@//Tools/Tophat:TophatExtension darwin_arm64-dbg-macos-arm64-min13.0-applebin_macos-ST-e022ee4a993b) is an app extension and requires `extension_host` to be set

The issue is that macos_extension does not support extension_host property. This issue is to track this working properly (whether that means adding extension_host in rules_apple or making this optional)

Reproduction steps

• Create a macos_extension
• Create a macos_aplication
• Add the extension to extensions of macos_application
• Try to generate a project with macos_application as a target

Expected behavior

This should work as expected without generation errors.

rules_xcodeproj version

2.x

Xcode version

1.61

Bazel version

7.4.1

rules_apple version

3.x

rules_swift version

2.x

Additional information

No response

Start with the reproduction steps and the related rules_xcodeproj issue #2937. Investigate how macos_extension targets are handled when included in a macos_application and how extension_host is expected to be supplied. Done means project generation succeeds for the stated macOS application and extension setup without the missing extension_host error.